Method and apparatus for forming contoured composite laminates

ABSTRACT

A composite laminate such as a hat-type stringer is formed on a contoured mandrel using a combination of mechanical sweeping and vacuum forming.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of prior co-pending U.S. patent application Ser. No. 14/279,725 filed May 16, 2014, issued as U.S. Pat. No. 9,782,937 on Oct. 10, 2017, the entire disclosure of which is incorporated by reference herein.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to the fabrication of composite structures, and deals more particularly with a method and apparatus for fabricating concave and convex stiffeners such as stringers, especially those that are contoured.

2. Background

Composite laminate structural stiffeners are sometimes required to have complex contours tailored to particular applications. For example, in the aircraft industry, composite laminate stringers used to stiffen aircraft skins are sometimes contoured in one or more planes in order to match changes in the geometry of the skins.

Layup and forming of structural stiffeners with complex contours can be challenging because of the tendency of the uncured composite prepreg material to bridge or wrinkle in the areas of contours. Dry fabric cloth used to make fiber performs that are subsequently infused with resin may also wrinkle when formed to a desired preform shape having contours, particularly when tackified and/or multiple plies of the cloth are being formed to shape simultaneously. Bridging results in undesired resin rich-areas in the laminate, while wrinkling may produce undesired localized high stress concentrations. In order to minimize these problems, composite laminate structural stiffeners such as stringers are usually laid up by hand in order to minimize bridging and wrinkling. However, even using hand layup techniques, bridging and wrinkling of the laminate sometimes occurs which requires hand rework of the stiffener, typically using patches. Hand layup of stiffeners and rework of stiffener non-conformities is both labor-intensive and time-consuming, and therefore expensive.

Accordingly, there is a need for a method and apparatus for laying up and forming contoured composite stiffeners such as composite laminate prepreg stringers, that reduce non-conformities and touch labor. There is also a need for a method and apparatus of the type mentioned above which may increase production throughput while reducing factory floor space required for stiffener production.

SUMMARY

The disclosed embodiments provide a method and apparatus for partially automating the fabrication of composite prepreg laminate stiffeners such as stringers, which reduces nonconformities and attendant rework, while reducing touch labor and increasing factory throughput. The disclosed method and apparatus employ a combination of mechanical sweeping and vacuum forming to form composite prepreg plies onto complex contours of a tool without substantial bridging or wrinkling.

According to one disclosed embodiment, apparatus is provided for forming plies of material onto a mandrel having contours. The apparatus includes a ply sweeper for sweeping the plies onto the contours of the mandrel, and a presser independently displaceable relative to the ply sweeper for pressing a portion of the plies against the mandrel. The apparatus further includes at least one powered actuator coupled with presser for displacing the presser relative to the ply sweeper.

According to another disclosed embodiment, apparatus is provided for forming composite plies on a mandrel contoured along its length and having a cap, a pair of webs, and a pair of flanges configured to form a hat-shaped stringer. The apparatus includes a frame, a ply sweeper, a presser and at least one linear actuator. The ply sweeper is mounted on the frame and is configured to sweep the composite plies down onto and over the webs of the mandrel. The presser is mounted on the frame and is extensible relative to the ply sweeper. The presser is configured to press a portion of the composite plies against the mandrel. The linear actuator is mounted on the frame and is coupled with presser for extending the presser relative to the ply sweeper.

According to still another disclosed embodiment, a method is provided of forming a composite stiffener contoured along its length. The method includes placing at least one composite ply over a mandrel and positioning a ply sweeper and a presser above the mandrel. The method also includes extending the presser relative to the ply sweeper using a linear actuator. The method further includes clamping a portion of the composite ply against the mandrel, including moving the presser and ply sweeper toward the mandrel until the presser forces a portion of the composite ply against the mandrel. The method also includes sweeping the composite ply down over the mandrel while the portion of the composite ply is clamped against the mandrel.

The features, functions, and advantages can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments in which further details can be seen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment of the present disclosure when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is an illustration of a perspective view of a composite prepreg laminate stringer having complex contours.

FIG. 2 is an illustration of a sectional view taken along the line 2-2 in FIG. 1 showing roll in the stringer, wherein the X-Y plane is indicated by a broken line.

FIG. 3 is an illustration of a sectional view taken along line 3-3 in FIG. 1, showing another roll in the stringer, wherein the X-Y plane is indicated by a broken line.

FIG. 4 is an illustration of a top plan view of the stringer shown in FIG. 1, showing changes in yaw.

FIG. 5 is an illustration of a side elevational view of the stringer shown in FIG. 1, showing changes in pitch.

FIGS. 6-12 are illustrations of cross-sectional views of apparatus for mechanical sweeping and vacuum forming composite prepreg plies on a mandrel having complex contours, respectively showing sequential forming steps.

FIG. 13 is an illustration of a side elevational view of a ply sweeper along with a vacuum bagged composite laminate ply.

FIG. 14 is an illustration of an isometric, cross sectional view taken along the line 14-14 in FIG. 13.

FIGS. 15-18 are illustrations of cross-sectional views of an alternate embodiment of apparatus for mechanical sweeping and vacuum forming composite plies on a contoured mandrel.

FIG. 19 is an illustration of a side elevational view of an alternate embodiment of a ply sweeper, portions of the ply sweeper having been broken away to reveal a spreader plate.

FIGS. 20 and 21 are illustrations of cross-sectional views showing the ply sweeper of FIG. 19 sweeping a ply over a contoured mandrel.

FIGS. 22-24 are illustrations of cross-sectional views showing an alternate embodiment of the ply sweeper progressively forming a ply over a contoured mandrel.

FIG. 25 is an illustration of a cross-sectional view showing another embodiment of the ply sweeper.

FIG. 26 is an illustration of a cross-sectional view showing a further embodiment of the ply sweeper in which the cap is pressed and fingers are held apart prior to sweeping.

FIG. 27 is an illustration of a cross-sectional view showing still another embodiment of the ply sweeper in which the sides of the cap presser are pulled toward one another as contact is made with the cap.

FIGS. 28 and 29 are illustrations of cross-sectional views showing a further embodiment of the ply sweeper progressively forming a ply over a contoured mandrel in which the finger halves are split.

FIG. 30 is an illustration of a cross-sectional view showing a further feature of the split finger ply sweeper in which the finger halves rotate to sweep the cap and cap/web outside radius prior to full engagement of the web/flange inside radius.

FIG. 31 is an illustration of a cross-sectional view showing an alternate embodiment of the apparatus for mechanically sweeping and vacuum forming plies on a contoured mandrel.

FIG. 32 is an illustration of an end elevational view of one embodiment of a forming unit for forming composite laminate prepreg plies on a mandrel contoured in one plane.

FIG. 33 is an illustration of an end elevational view of another embodiment of a forming unit for forming composite laminate prepreg plies on a mandrel contoured in multiple planes.

FIG. 34 is an illustration of a combined block and diagrammatic view of forming apparatus employing the forming units of the FIG. 33 arranged side-by-side.

FIG. 35 is an illustration of an end elevational view of a mobile cart interfacing with a forming station.

FIG. 36 is an illustration of a combined block and diagrammatic view of forming apparatus employing the mobile cart and forming station shown in FIG. 35.

FIG. 37 is an illustration of a perspective view of an alternate form of a forming apparatus.

FIG. 38 is an illustration of a side elevational view of one of the former modules shown in FIG. 37.

FIG. 39 is an illustration of a front perspective view of the forming apparatus shown in FIG. 37.

FIG. 40 is an illustration of an isometric view of a portion of the forming apparatus shown in FIGS. 37 and 39.

FIG. 41 is an illustration of a flow diagram of a method of forming contoured composite prepreg plies.

FIG. 42 is an illustration of a flow diagram of a method of forming contoured composite prepreg stringers.

FIG. 43 is an illustration of a flow diagram of a method of laying up and forming composite prepreg laminate stiffeners.

FIG. 44 is an illustration of a side view of an alternate embodiment of the forming head.

FIG. 45 is an illustration of the area designated as “FIG. 45” in FIG. 44.

FIG. 46 is an illustration of an end view of the forming head shown in FIG. 44.

FIG. 47 is an illustration of a perspective view of a portion of the forming head of FIG. 44, showing the presser engaging the cap section of a fully formed and compacted stiffener.

FIG. 48 is an illustration of a perspective view of a presser section.

FIG. 49 is an illustration of an elevational view of one and of the presser section of FIG. 48.

FIG. 50 is an illustration of an elevational view of the other end of the presser section of FIG. 48.

FIG. 51 is an illustration of a side elevational view showing a joint between two of the presser sections.

FIG. 52 is an illustration of a top plan view of the joint between the presser sections shown in FIG. 51.

FIG. 53 is an illustration of an end view of the forming head, aligned above a mandrel in preparation for carrying out forming operation.

FIG. 54 is an illustration similar to FIG. 53 but showing forming head having descended toward the mandrel, causing the presser to clamp a portion of a ply on the Of the mandrel.

FIG. 55 is an illustration of the area designated as “FIG. 55” in FIG. 54.

FIGS. 56-58 are illustrations similar to FIG. 53, showing sequential forming of the plies.

FIG. 59 is an illustration of a combined block and diagrammatic view of a system for controlling multiple forming heads used to form a contoured composite stiffener.

FIG. 60 is an illustration of a flow diagram of a method of forming a composite stiffener contoured along its length.

FIG. 61 is an illustration of a flow diagram of aircraft production and service methodology.

FIG. 62 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIGS. 1-5, the disclosed embodiments relate to a method and apparatus for laying up, forming and handling a composite prepreg structure such as a multi-ply laminate stiffener. The stiffener may be, for example, a contoured composite stringer 50. The stringer 50, sometimes referred to as a hat stringer 50 includes a cap 56, a pair of webs 58, and a pair of flanges 54. An inside radius 60 joins the web and flange surfaces. While a hat type stringer 50 is illustrated, a wide variety of other cross-sectional stiffener shapes may be formed by the disclosed method and apparatus discussed below. The stringer 50 is formed from laminated plies of a fiber reinforced polymer resin such as, without limitation, carbon fiber epoxy. In one example, the stringer 50 may be fabricated using plies of unidirectional prepreg that are laid up and formed individually, or in groups (i.e., multiple plies).

The stringer 50 may have one or more complex contours along its length. Any of these contours may be constant or varying. For example, the illustrated stringer 50 has curvatures (see FIGS. 1 and 4) in the X-Y plane, and curvatures (FIG. 5) in the X-Z plane. Portions of the stringer 50 may also be twisted at a constant or varying angle θ (FIGS. 2 and 3) in the Y-Z plane. For ease of description hereinafter, curvature in the Y-Z plane will be referred to roll (twist), curvature in the X-Z plane will be referred to as pitch, and curvature in the X-Y plane will be referred to as yaw.

Referring now to FIG. 6, at least one flat ply 82 of material may be laid up and formed on a layup tool such as an elongate mandrel 74 mounted on a tool base 84. The mandrel 74 is contoured along its length as well as contoured transversely. In one example, the ply of material, sometimes referred to herein as a composite or prepreg ply 82, may comprise a unidirectional or bi-directional fiber reinforcement impregnated with and held in a suitable resin matrix such as a thermoset or a thermoplastic. In another example, the ply 82 may be a dry fiber or a tackified fiber reinforcement which is infused with a resin after the ply has been formed to the desired preform shape. The mandrel 74 has an outer contoured surface comprising a first portion and a second portion. The first portion of the contoured mandrel surface comprises a cap section 76, a pair of web sections 78, and inside radii 90. A second portion of the contoured mandrel surface comprises a pair of flange sections 80. The cap section 76, web sections 78, inside radii and flange sections 80 all have substantially the same size, shape and location as the IML (inner mold line) of the stringer 50 shown in FIGS. 1-5.

As will be discussed below in more detail, at least one ply 82 is laid up and formed on the mandrel 74 using a two-step process comprising mechanical sweeping and vacuum forming. The mechanical sweeping of the ply is performed by a forming head 64 which is stroked down over the web sections 78, and the vacuum forming is performed by a vacuum membrane such as, without limitation, a flexible diaphragm 86. As will become apparent later in the description, any of a variety of mechanisms and techniques may be employed to perform the mechanical sweeping and the vacuum forming. As previously noted, in some embodiments, multiple plies 82 may be simultaneously laid up and formed on the mandrel 74.

The forming head 64 includes a ply sweeper 65 which may comprise a plurality of longitudinally spaced mechanical forming fingers 66 that are arranged in opposing sets thereof. In one embodiment, the forming fingers 66 may be formed of a flexible, resilient material such as plastic, composite, metal etc. The ply sweeper 65 is mounted by suitable hardware 68 to a ram which may comprise, for example and without limitation, a pneumatic piston rod 70. The piston rod 70 drives the ply sweeper 65 downwardly 72, causing the forming fingers 66 to initially clamp the ply 82 on the cap section 76 in order to maintain alignment of the ply 82 relative the mandrel 74 during the subsequent forming process. Continued downward movement of the piston rod 70 causes the forming fingers 66 to deflect outwardly while maintaining pressure against the ply 82, thereby sweeping the ply 82 down over, and conforming to the web sections 78 of the mandrel 74.

The flexible diaphragm 86 is disposed between the mandrel 74 and the forming head 64. The diaphragm 86 is sealed around its periphery to the tool base 84 by seals 88, forming a substantially vacuum tight chamber around the flange sections 80. The diaphragm 86 may be formed of a suitable material such as reinforced latex, silicone or the like which, while flexible, is substantially stretchable only in one direction (in the direction of the X-axis). In some embodiments, the diaphragm 86 may be a separate element that is manually placed between the forming head 64 and the mandrel 74. Alternatively, the diaphragm 86 along with one or more plies 82 adhered to it may be shuttled together between the forming head 64 and the mandrel 74. In other embodiments, however, the diaphragm 86 may be attached to, and form a part of the forming head 64. In still other embodiments discussed later herein, the diaphragm 86 may comprise an encapsulating membrane, such as tube-type flexible vacuum bag that surrounds the ply layup.

The sequential steps of forming the ply 82 are illustrated in FIGS. 7-12, according to one method embodiment. Initially, as shown in FIG. 7, with the tips 75 of the fingers 66 spread apart sufficiently to clear the cap section 76, the forming head 64 is displaced downwardly 72, causing the fingers 66 to initially clamp a portion of the diaphragm 86 and ply 82 against the cap section 76 of the mandrel 74. With the ply 82 clamped against the cap section 76, and therefore immobilized, the forming head 64 continues its downward displacement 72, causing the fingertips 75 to apply pressure to and form the ply 82 down against the web sections 78 of the mandrel 74, as shown in FIG. 8.

Continued downward movement 72 of the forming head 64, shown in FIGS. 9 and 10, causes the ply sweeper 65 to form the ply 82 against the remaining portions of the web sections 78 until the fingertips 75 reach the inside radii 90 (FIG. 10). At this point, both the cap 56 and the webs 58 of the stringer 50 fully match the geometry of the web sections 78 of the forming mandrel 74. Next, shown in FIG. 11, with the fingertips holding the ply 82 against the mandrel 74 at the inside radii 90, the diaphragm 86 is sealed to the tool base 84, and then evacuated using a vacuum source 94 to draw air through openings 92 in the tool base 84.

Referring to FIG. 12, the evacuation of the diaphragm 86 causes the diaphragm 86 to draw the ply 82 down against the flange sections 80 of the mandrel 74, thereby completing matching the geometry of the flange sections 80 of the forming mandrel 74. With the shape of the stringer 50 having been fully formed, the forming head 64 is raised, and the diaphragm 86 is drawn away, permitting removal of the fully formed stringer 50 from the mandrel 74. In some embodiments, as will be discussed below in more detail, the mandrel 74 may also be employed to transport and place the completed stringer 50 onto a cure tool (not shown) for curing.

FIGS. 13 and 14 illustrate an embodiment of the ply sweeper 65 comprising a tube 96 having a plurality of longitudinally spaced slots 98 therein which define two sets of opposing, flexible forming fingers 100. The tube 96 may be formed of a flexible, resilient material such as, without limitation, plastic, and the slots 98 may be formed using any suitable fabrication process such as sawing or cutting. The opposed flexible fingers 100 have fingertips 102 that are spaced apart sufficiently to clear the cap section 76, as best seen in FIG. 14. In the embodiment illustrated in FIGS. 13 and 14, a tube-type vacuum bag 105 (shown in FIG. 13 only) is sleeved over the plies 82 and the mandrel 74.

When evacuated, the tube-type vacuum bag 105 vacuum forms the plies 82 down onto the flange sections (FIG. 12) of the mandrel 74. In some embodiments, compliance of the tube 96 to the shape of the mandrel 74 may be achieved by dividing the tube 96 into a plurality of individual sections, each adjustable to match local contours of the mandrel 74. In other embodiments, however, a single tube 96 extending along the entire length of the mandrel 74 may be employed to perform the sweeping action. Where a single tube 96 is used, the necessary compliance of the tube 96 to changing mandrel contours (roll, pitch and yaw) may be obtained by providing the top 97 of the tube 96 with flexibility, either by segmenting the top 97 of the tube 96, or by forming the top 97 of the tube 96 from a flexible material such as a rubber.

Depending upon the type of ply sweeper 65 being employed, it may be necessary to spread the fingertips 102 a distance that is greater than the width of the cap section 76 of the mandrel 74. One device for spreading or opening the fingertips 102 is shown in FIGS. 15-18. Referring to FIG. 15, an inflatable bladder 104 is disposed inside the tube 96, as shown in FIGS. 13 and 14. The bladder 104 may be inflated using any suitable pressurized fluid, such as air. With the bladder 104 fully inflated, as shown in FIG. 15, a lower portion 104 a of the bladder 104 extends below the fingertips 102.

Referring to FIG. 16, as the forming head 64 is displaced downwardly, the lower portion 104 a of the bladder 104 initially contacts the ply 82, clamping it against the cap section 76 of the mandrel 74 in order to maintain alignment of the ply 82 relative to the mandrel during the subsequent forming process. When the fingertips 102 clear the cap section 76 and began forming the ply 82 against the web sections 78, the bladder 104 is deflated, as shown in FIG. 17, permitting the finger forming process to continue. The bladder 104 remains substantially deflated until the fingertips 102 have formed the ply 82 down into the inside radii 90, as shown in FIG. 18.

Other techniques may be employed, where necessary, to spread the fingertips 102 a distance that is sufficient to clear the cap section 76 of the mandrel 74. For example, referring to FIG. 19, a longitudinally extending spreader plate 110 may be installed inside the tube 96 and used to open the fingers 100. The spreader plate 110 has threaded studs 106 that pass through the top of the tube 96. Wingnuts 108 or similar fasteners on the threaded studs 106 may be adjusted to alter the vertical position of the spreader plate 110. In some embodiments, a power operated device such as a pneumatically or electrically driven screw drive (not shown) may be employed in lieu of the wing nuts 108 to provide automated adjustment of the position of the spreader plate 110. Referring to FIG. 20, as the spreader plate 110 is drawn upwardly in response to adjustment of the wingnuts 108, the spreader plate 110 engages the inner diameter of the tube 96, forcing the opposing sets of fingertips 102 to spread 114 until they clear the cap section 76 the mandrel 74. Continued downward movement of the tube 96 (see FIG. 21) allows the fingertips 102 to complete forming of the web sections 58 of the stringer 50.

FIGS. 22-24 illustrate another embodiment of the sweeper 65 having forming fingers 100 similar to those previously described. In this embodiment, movable forming elements 116 are captured between the fingertips 102 and the ply 82. The forming elements 116 have flat surface areas 116 a that engage a greater surface area of the ply 82, compared to the embodiments shown in FIGS. 19-21 in which only the outer ends of the fingertips 102 engage the ply 82. As the tube 96 is displaced downwardly, as shown in FIG. 23, the forming elements 116 pivot relative to the fingertips 102, forcing the ply down against the web sections 78 of the mandrel 74. The forming elements 116 continue pivoting until they form the ply 82 down into the inside radii 90, as shown in FIG. 24.

A variety of other techniques may be employed to clamp the ply 82 to the cap section 76 in order to maintain alignment of the ply 82 relative to the forming mandrel 74 as the ply 82 is being formed. For example, referring to FIG. 25, a clamping element 120 is mounted on the end of a rod 118 that passes through the top of the tube 96. Downward displacement of the rod 118 brings a clamping element 120 into contact with the ply 82, forcing the ply 82 against the cap section 76. With the ply 82 clamped against the cap section 76, the tube 96 is displaced downwardly relative to the rod 118, allowing the forming fingers 100 to sweep the ply 82 over the web sections 78.

FIG. 26 illustrates another embodiment of the forming head 64 in which clamping of the ply 82 to the cap section 76 is performed by a spring-loaded clamping member 124 having a clamping surface 128 that is approximately the same width as the cap section 76. The clamping member 124 may comprise, for example and without limitation, rigid plastic having a hollow core. The use of a relatively broad clamping surface 128 may assist in maintaining the cap 56 relatively flat during the forming process. The clamping member 124 is attached to a rod 122 surrounded by a compression spring 126 that is trapped between the clamping member 124 and the inside surface of the tube 96. As the forming head 64 moves downwardly, the clamping member 124 makes initial contact with the ply 82.

Continued downward movement of the forming head compresses the spring 126, which in turn loads the clamping member 124 against the ply 82 and the cap section 76. As the tube 96 continues its downward movement, the fingers 100 sweep the ply 82 over the web sections 78, and the rod 122 is allowed to move up through the top of the tube 96. In some embodiments, as shown in FIG. 27, it may be necessary or desirable to place a membrane over the bottom of the clamping member 124 to assist in flexing the sides of the clamping member 124 toward the webs as the cap is clamped, further providing a smooth transition of the fingers from the sides of the clamping member 124 to the webs 78.

Attention is now directed to FIGS. 28 and 29 which illustrate another embodiment of the forming head 64 which utilizes a cam mechanism 132 for controlling the position of the forming fingers 100 during the ply sweeping process. The cam mechanism 132 comprises a cam member 138 wedged between a pair of a pair of spreader blocks 134, 136 which act as cam followers that are displaced by downward movement of the cam member 138. The spreader blocks 134, 136 are respectively attached to two sets of independent and opposing forming fingers 100. The spreader blocks 134, 136 are spring-loaded 135 toward each other, causing fingers 100 to normally spread apart. However, pressure applied to the spreader blocks 134, 136 by the cam member 138 overcomes the force of the spring-loading, forcing the fingers 100 toward each other.

FIG. 28 shows the fingertips 102 spread apart a distance that is sufficient to clear the cap section of the mandrels 74. Downward movement the cam member 138 (see FIG. 29) causes the fingertips 102 to move toward each other and sweep ply 82 onto the web sections 78 as the forming head 64 moves downwardly. While a cam mechanism has been disclosed, a variety of other known mechanism may be employed to control the position of the forming fingers 100 during the ply sweeping process.

Attention is now directed to FIG. 30 which illustrates another embodiment of the forming head 64 which employs a link mechanism 137 for controlling the movement of fingers 100 during a ply sweeping operation. A drive link 131 is pivotally connected to one end of each of two connecting links 139, 141. The other ends of the connecting links 139, 141 are respectively pivotally connected to a pair of spreader blocks 134, 136 that are fixed to two separate, opposed sets of the forming fingers 100. A downward force F applied to the drive link 131 is transmitted through the connecting links 139, 141 to the fingers 100. The fingers 100 rotate 143 in response to the force applied by the connecting links 139, 141, thereby controlling the movement of the fingertips 102 during sweeping of a ply 82 down over the web sections 78 of the mandrel 74. A pair of blocks 145 act as stops that engage the spreader blocks 134, 136 to limit the rotation of the fingers 100.

FIG. 31 illustrates an alternate embodiment of a forming apparatus, in which the force used to displace the sweeper 65 is supplied by an outer diaphragm or vacuum bag 142. In this embodiment, the mandrel 74 is mounted on a tool base 140, along with a pair of sealing blocks 148. Each of the sealing blocks 148 extends longitudinally along the outer edges of the flange sections 80 and includes inner and outer seal surfaces 150, 152. An inner diaphragm 86 (discussed previously) is placed over a ply 82 and is adapted to be sealed against the inner seal surface 150. The outer diaphragm 142 covers the forming head 64 and is sealed to the outer seal surface 152 of blocks 148, forming a vacuum tight outer chamber 167. A caul plate 144 may be placed between the ply sweeper 65 and the outer diaphragm 142 in order to concentrate and direct pressure P from the outer diaphragm 142 onto the ply sweeper 65. A pair of vacuum lines 162, 164 pass through the mandrel 74 and are adapted to evacuate the area beneath the inner diaphragm 86. A third vacuum line 170 is coupled through a valve 168 to both the ambient atmospheric air 166 and the vacuum regulator 156. The vacuum line 170 passes through one of the blocks 148 and communicates with outer chamber 167 beneath the outer diaphragm 142.

In operation, a ply 82 is placed over the mandrel 74, and the inner diaphragm 86 is placed over ply 82 and sealed to the inner seal surfaces 150. The outer diaphragm 142 along with the forming head 64 is then positioned over the mandrel 74, and the outer diaphragm 142 is sealed to the outer seal surfaces 152. A partial vacuum is then drawn on both the inner and outer diaphragms 86, 142 respectively, using vacuum lines 164, 170. The partial vacuum in the outer chamber 167 produces a pressure P that forces the forming head 64 downwardly, causing the fingertips 102 of the ply sweeper 65 to form the ply 82 down over the web sections 78 of the mandrel 74.

When the fingertips 102 bottom out at the inside radii 90, a hard vacuum is pulled on the inner diaphragm 86 while the partial vacuum on the outer diaphragm 142 is released through vacuum line 170 and valve 168. The hard vacuum pulled on the inner diaphragm 86 forms the ply 82 down onto the flange sections 80 of the mandrel 74. In order to assist in removing the sealed inner diaphragm 86, positive pressure may be applied to the inner diaphragm 86 using the line 162. The inner and outer diaphragms 86, 142, along with the forming head 64 are then removed to allow the fully formed ply 82 to be removed from the mandrel 74.

It should be noted here that, as previously mentioned, other techniques and mechanisms can be employed to actuate a stroke of the forming head 64 such as, without limitation, clamps, pneumatic cylinders, threaded screw drives, robots, hoses and outer diaphragms, to name only a few.

Attention is now directed to FIG. 32 which illustrates a portable forming unit 172 that may be used to form a portion of the length of a contoured composite laminate stringer 50. As will be discussed below in more detail, a plurality of the forming units 172 may be assembled side-by-side to form various portions of the stringer 50 which respectively may have differing contours. In the example illustrated in FIG. 32, one or more composite laminate plies (not shown in FIG. 32) are formed on a mandrel 74 having one or more contours in the X-Z plane in order to form a composite laminate stringer 50 having variations in pitch. In other embodiments, the mandrels 74 may have one or more contours in the X-Y plane (variations in yaw), and/or one or more contours in the Y-Z plane (variations in roll).

The portable forming unit 172 broadly comprises a former module 174 mounted on a movable platform, which in one embodiment, may comprise a mobile cart 188. Other forms of movable platforms are possible, depending on the application. The former module 174 includes a C-shaped frame 175 having a vertical support 176, an upper arm 178, and a lower arm 180. The former module 174 also includes a forming head 64 mounted on a piston rod 184 of a cylinder 182 for movement along the Z-axis. The cylinder 182 may be, for example and without limitation part of a hydraulic or pneumatic powered cylinder. The mandrel 74 is removably mounted on the lower arm 180 by any suitable means, such as a hand operated clamp (not shown).

The mobile cart 188 comprises an upright member 190 on which the vertical support 176 is mounted, as well as a cart base 192 having wheels 194 that allow the cart 188 to be moved over a supporting surface such as a factory floor (not shown). An adjustment mechanism 165 is provided for adjusting the position and orientation of the former module 174 on the upright 190 for movement along the Z axis. In one embodiment, the adjustment mechanism 165 may comprise a screw drive 196 that may be manually or power driven to adjust the orientation of the former module 174 to match the contour of local sections of the mandrel 74.

FIG. 33 illustrates an alternate embodiment of a forming unit 172 that includes independent adjustment of the roll, pitch and yaw of a forming head 64, thereby allowing a composite laminate stringer 50 to be formed that has complex contours, such as the stringer shown in FIGS. 1-5. The forming unit 172 shown in FIG. 33 is similar to that shown in FIG. 32, but additionally has adjustment mechanisms 165 for adjusting the pitch (X-Z plane), roll (Y-Z plane) and yaw (X-Y plane) of the forming head 64. The adjustment mechanism 165 includes screw drives 198, 206 and 208. Roll of the entire former module 174 may be adjusted using screw drive 206, 208 to adjust the position of slides 202, 204 that support the C-shaped frame 175 on a cart upright 190. The yaw of the former module 174 may be adjusted using screw drive 198 to rotate the C-shaped frame 175 on the cart upright 190. It should be noted here that various alternate mechanisms may be used to adjust the yaw, pitch and/or roll of the forming head 64 relative to the mandrel 74, and any or all of these mechanisms may be part of the forming head 64, or part of the former module 174 or part of the cart 188. The adjustment mechanisms described above provide a form of passive compliance that permits the sweeper 65 to be aligned with local contours of the mandrel 74.

A plurality of the forming units 172 of the type shown in FIGS. 32 and 33 may be assembled together to collectively form an apparatus for forming a composite prepreg laminate having complex contours. For example, referring to FIG. 34, a forming apparatus 195 comprises a plurality of the forming units 172 arranged side-by-side which may be mechanically connected together by suitable mechanical interlocks 185. Each of the forming units 172 is aligned with local contours of the forming mandrel 74 and is operative to form a section of the prepreg laminate. Each of the forming units 172 comprises a former module 174 that is associated with a section of the mandrel 74 and is mounted on a mobile cart 188, or similar mobile platform. Each of the former modules 174 includes the previously discussed features necessary to permit adjustment of yaw, pitch and roll of the forming head 64 to substantially match the local contouring of the mandrel 74. The number of the forming units 172 assembled together will depend upon the length of the particular layup mandrel 74 being employed. The use of the individual forming units 172 permits the forming units 172 to be readily interchanged, for repair or service, and provides the flexibility to add or remove forming units 172, as required to suit the particular application.

Attention is now directed to FIGS. 35 and 36 which illustrate apparatus 205 useful in layup, forming, handling and installation of composite prepreg laminates such as stringers. The apparatus 205 broadly comprises one or more forming stations 226, and one or more interfacing mobile carts 214. Each of the forming stations 226 includes a former module 240 provided with a forming head 64 and a mechanism 165 for adjusting the roll, pitch and/or yaw of the forming head 64 to match local contours of a mandrel 74, similar to the embodiments previously described. The former module 240 is mounted on a frame assembly 235 comprising uprights 234 and a series of cross members 228, 230, 232. The frame assembly 235 may be provided with wheels 194 to facilitate portability of the forming station 226.

Each of the mobile carts 214 comprises a mandrel support table 216 on which at least a portion of a mandrel 74 may be supported. The spacing between adjacent ones of the support tables 216 substantially matches the spacing between adjacent ones of the former modules 240, such that each of the support tables 216 is aligned with one of the former modules 240. The support table 216 is mounted on one or more uprights 190. The uprights 190 are attached to vertical frame members 220 that are supported on a base 192 having wheels 194. The uprights 190 are vertically slidable on the frame members 222 allow the vertical height of the support table 216, and thus of the mandrel 74 to be adjusted.

In use, the mandrel 74 may be placed on the support table 216 of one or more of the mobile carts 214, and the carts 214 may be rolled 224 into the forming station 226, such that the mandrel 74 is aligned beneath the forming head 64. Alternatively, the mandrel 74 may be placed on the carts 214 after the latter have been rolled 224 into the forming station 226. In order to maintain alignment of forming head with the mandrel 74, a mechanical interlock 185 may be provided between the forming station 226 and the mobile cart 214. After one or more prepreg plies have been laid up and formed in the forming station 226, the cart 214 may be used to transport the fully formed stringer to another processing station where the carts 214 may be used to handle or manipulate the stringer. For example, the carts 214 may be used to install the formed stringer in a cure tool (not shown).

Attention is now directed to FIGS. 37-40 which illustrate another embodiment of the former apparatus 244 which employs features of the embodiments previously discussed. The apparatus 244 comprises a plurality of individual former modules 174 mounted on a common base, which in illustrated embodiment, comprises a center support beam 262. The center beam 262 may be supported on one or more sets of wheels 260 which provide the former apparatus 244 with mobility.

Each of the former modules 174 comprises a forming head 64 supported on a C-shaped frame 246. The C-shaped frame 246 includes an upright 248, a lower arm 250 and an upper arm 252. A contoured mandrel 74 is removably mounted on the lower arms 250 (FIG. 37) by any suitable mechanism, such as hand clamps 266. Each of the C-shaped frames 246 is mounted on the center beam 262 by a pair of vertical supports 264. The vertical supports 264 are adjustably connected between the lower arm 250 and the center beam 262 by a series of brackets 268 and fasteners 269 received within ways 270 forming slides. The fasteners 269 (see FIG. 40) selectively fix the brackets 268 in any desired adjustment position. Adjustment of the position of brackets 268 in turn allows adjustment of the position of the C-shaped frame 246, and thus of the forming head 64, in both the Y-Z (roll) and X-Z (pitch) planes. Guide rails and linear actuators (not shown) may be employed for moving and adjusting the vertical supports 264 and the lower arm 250.

Each of the forming heads 64 may comprise a ply sweeper 65 attached to an assembly bar or frame 254 which is secured to the lower end of a guide rail 256. The individual ply sweepers 65 (tubes 96) are linked together by the C-shaped frames 246 and the center support beam 262. The adjustability of the C-shaped frames 246 provides the apparatus 244 with passive compliance which allows adjustment of the sweepers 65 to match local contouring of the mandrel 74. The guide rail 256 is mounted for linear movement along the Z-axis on the outer end of the upper arm 252 by two sets of guide rollers 258. A double acting pneumatic drive cylinder 182 mounted on the upper arm 252 has a piston rod 184 attached to the forming head 64. The cylinder 182 displaces the forming head 64 during the forming process, guided by the rail 256. In the illustrated embodiment, the ply sweeper 65 comprises a plurality of forming fingers on a tube 96, however, other embodiments of the ply sweeper 65 previously discussed may be used.

Reference is now made to FIG. 41 which broadly illustrates the overall steps of a method of forming a contoured composite prepreg laminate, such as the stringer 50 shown in FIGS. 1-5. Beginning at step 278, at least one ply 82 of material such as a prepreg is placed on a contoured mandrel 74. Then, at step 280, the prepreg ply 82 is mechanically swept over a first section of the contoured mandrel 74. Finally, at 282, the prepreg ply 82 is then vacuum formed over a second section, also referred to as the flange sections 80 of the contoured mandrel 74.

FIG. 42 broadly illustrates the overall steps of a method of forming a composite prepreg, hat-type stringer 50. Beginning at 284, at least one prepreg ply is placed on a contoured mandrel 74. At 286, the prepreg ply 82 is secured on a cap section 76 of the contoured mandrel 74. At step 288, the prepreg ply 82 is swept over web sections 78 of the contoured mandrel 74. At 290, the prepreg ply 82 is held against the inside radii 90 of the contoured mandrel 74. With the prepreg ply 82 held against the inside radii 90, then, at step 292, the prepreg ply 82 is then vacuum formed over flange sections 80 of the contoured mandrel 74.

Attention is now directed to FIG. 43 which illustrates a further embodiment of a method of laying up and forming highly contoured composite laminate stiffeners, such as a stringer 50. At 294, one or more plies 82 are laid down on the mandrel 74 and swept over the cap section 76. Heat may be applied to the plies 82, as required, to soften the plies 82 in preparation for forming, and/or to assist in tacking them to the cap section 76. Next, at 296, the plies 82 are encapsulated in a vacuum membrane, such as a flexible tube bag 105.

At 298, the mandrel 74 having the plies laid up thereon is transferred to and mounted in a former apparatus 244. At 300, each of the forming heads 64 of the apparatus 244 is aligned with the cap section 76 of the mandrel 74. At step 302, a release film such as permeable Armalon® is installed over the encapsulated plies 82. In some embodiments, the Armalon® may be integrated into or removably attached to the former module 174, thus eliminating the need to perform step 302.

At 304, optionally, the forming fingers 102 are opened a distance that is sufficient to clear the cap section 76. At 306 forming fingers 100 are used to sweep the ply 82 over the web/flange radius of the mandrel 74. At 308, the forming fingers 100 are used to hold the plies 82 at the inside radii 90 of the mandrel 74. At 310, vacuum is applied to the bag, resulting in the plies being vacuum formed down onto the flange sections 80 of the mandrel 74. At step 312, the forming fingers 100 are retracted while vacuum is maintained against the plies 82.

The method described above in connection with FIG. 43 involves sweeping and then vacuum forming each ply 82. Other words, the plies 82 are fully formed one-by-one onto all sections of the mandrel 74.

Alternatively, in another embodiment, multiple plies, or all of the plies may be swept over the web/flange radius before the flange sections 80 are vacuum formed. Once the multiple plies have been formed over the web/flange radius, then the entire group of plies is vacuum formed in order to form the flange sections 80. In other words, the vacuum forming of the plies 82 down onto the flange sections 80 is performed only after all of the plies 82 have been swept over the web/flange radius.

Attention is now directed to FIGS. 44-47 which illustrate an alternate embodiment of the forming head 64 comprising a ply sweeper 65 and a presser 316 mounted on a frame 254. The frame 254 is fixed on the lower end of a guide rail 256 similar to the guide rail 256 forming part of the former module 174 previously described connection with FIGS. 37-39. The frame 254 and the guide rail 256 are vertically displaceable by pneumatic cylinder 182 (see FIG. 39). The cylinder 182 includes a piston rod 184 that is attached to the guide rail 256 by a bracket 314. As will be discussed below in more detail, the presser 316 is vertically displaceable independent of the vertical displacement of the ply sweeper 65. In other words, the presser 316 may be displaced relative to the ply sweeper 65. It should be noted here that while only a single forming head 64 is illustrated in FIGS. 44-47, multiple forming heads 64 of this embodiment can be employed in connection with the apparatus 195 shown in FIGS. 34-40 to form plies 82 on long mandrels 74. As will be discussed below, in an application where multiple forming heads 64 employed to form long stringer 50, the pressers 316 of the forming heads 64 are connected together to form one continuous presser 316 having sufficient compliance to conform to the contours of the mandrel 74 along its length.

As best seen in FIGS. 46 and 47, in this embodiment, the ply sweeper 65 comprises separate sets of curved, flexible forming fingers 100 respectively secured to opposite sides of the frame 254. The forming fingers 100 terminate in fingertips 102 which are slightly spaced apart to form an opening 344 which extends along the length of the ply sweeper 65. A pair of spaced apart, linear actuators 318 such as double acting pneumatic cylinders, or similar motor members, are mounted on the frame 254 and each include a displaceable piston rod 320 that extends downwardly through the frame 254, between the opposing sets of fingers 100, and passes through the opening 344 between the fingertips 102.

The lower ends of the piston rods 320 are connected to the presser 316 by couplings 321. Each of the couplings 321 comprises a clevis 322 provided with a clevis pin 324 that forms a pivotal connection 330 between the ends of the piston rods 320 and a longitudinal rib 332 forming part of the presser 316. The clevis pin 324 is slidable within a slotted hole 328 in the presser 316. The combination of the pivotal connection 330 and the slotted hole 328 allow the presser 316 to both locally rotate (pivot) 329 and axially slide 326, thereby giving the presser 316 the ability to conform to contours along the length of contoured mandrel (see FIG. 53) on which plies 82 are formed. The ability of the presser 316 to conform to the contours of the mandrel 74 along its length allows a single presser 316 to be used to form plies 82 on variety of mandrels 74 that respectively have different contours. It should be noted here that while two linear actuators 318 are illustrated, as few as one or more than two linear actuators 318 may be employed to displace the presser 316 relative to the ply sweeper 65. As will be discussed later, the amount of force applied by the liner actuators 318 to the presser 316 may be varied during a forming operation.

Referring now to FIGS. 46-50, the presser comprises a backbone-like central rib 332 to which the lower ends of the piston rods 320 are pivotally connected as previously described. The presser 316 further includes flexible features in the form of a pair of outwardly extending, downwardly turned flexible wings 334. A foot 335 on the bottom of the rib 332 extends between the two wings 334 and is shaped to match certain features of the mandrel, which in the illustrated example, comprises the flat cap section 76 of a mandrel 74 that is configured to form a hat-shaped stringer having a flat cap. Where the stringer is to have a curved or domed cap, the foot 335 of the presser is cured to match the curvature of the dome section of the stringer hat. The distance “D” between the outer extremities of the wings 334 is slightly greater than the width of the cap section 76, and the thickness “T” and height “H” of the rib 332 will depend upon application. The height “H” is dependent in part on the selection of the material used to fabricate the presser 316 as well as its required stiffness. The presser 316 is formed of a material such as a flexible plastic or rubber which has sufficient rigidity to transfer the necessary forming loads evenly along its length between support points without bridging due to local geometry changes of the mandrel 74. However, the presser 316 has sufficient flexibility to enable it to flex, deform and conform to the contours of the mandrel 74, avoiding any bridging over contours in the mandrel 74. While in the illustrated embodiment, the presser 316 is flexible to allow it to take the shape of the contoured mandrel 74, in other examples, the presser 316 can be substantially inflexible, i.e. rigid, and contoured to match the contour of the mandrel 74.

Referring now also to FIGS. 51 and 52, in applications where the presser 316 is used to form a long composite part, such as a contoured stringer requiring the use of multiple former modules 174 (see FIG. 37) and corresponding forming heads 64, the presser 316 comprises a plurality of presser sections 316 a fastened together and arranged end-to-end to form a single, continuous presser 316 which is conformable along its length to the contours of the mandrel 74. The opposite ends of the presser sections 316 a are provided with laps 336 and fastener holes 341. The presser sections 316 a are assembled end-to-end such that the laps 336 form half lap splice joints 342 between adjacent presser sections 316 a. The ends of the presser sections of 316 a are fixed to each other using fasteners (not shown) passing through the fastener holes 341.

FIGS. 53-58 sequentially illustrate the movements and operation of the forming head 64 during a forming operation in which a contoured composite part, such as a stringer or other stiffener is formed to shape. Referring to FIG. 53, one or more plies 82 are placed over a mandrel, which in the example, has a hat shape cross-section and includes flange sections 80. The plies may be a woven or knitted cloth that are used to produce a fiber preform that is subsequently infused with a suitable resin prior to curing. In other examples, the plies 82 may comprise a prepreg employing a material system that is suitable for the application using one or more types of woven, knitted or unidirectional reinforcing fibers held in a thermoset or a thermoplastic resin matrix. After positioning the plies 82 over the mandrel 74, the combination of the mandrel 74 and plies 82 are enclosed in a sealed vacuum bag 105 which is later evacuated during the forming operation. The forming head is vertically aligned above the centerline of the mandrel 74, with the piston rod 320 fully extended to position the presser 316 immediately beneath the fingertips 102 of the ply sweeper 65.

Next, as shown in FIG. 54, the entire forming head 64 is displaced downwardly, driven by the pneumatic cylinder 182 (FIG. 37) which forms part of a former module 174. As the presser 316 approaches the mandrel 74 during this downward displacement, the wings 334 of the presser 316 engage the cap section 76 and/or the web sections 78 of the mandrel 74, producing a lateral force that assists in centering the forming head 64 relative to the centerline of the mandrel 74, while forming the ply over upper areas of the web sections of 78 of the mandrel 74. The passive, self-aligning function provided by the wings 334 may eliminate the need for other mechanisms such as N/C driven devices, to precisely align the forming head 64 relative to the mandrel 74, resulting in greater reliability and effectiveness of the forming fingers 100 in forming the plies 82 down onto the mandrel 74. As the presser 316 continues moving down, the foot 335 of the presser 316 engages a portion of the ply 82 and clamps it against the cap section 76 of the mandrel 74, thereby preventing the ply 82 from shifting laterally during the remainder of the forming process. The amount of clamping force applied to the ply in this manner is controlled by the linear actuators 318. The amount of force applied to the presser 316 by the linear actuators 318 can be controlled during the forming sequence, unlike springs or other simple mechanisms used to load the presser 316. Consequently, for example, maximum force can be applied by the actuators 318 to the presser 316 before the finger 100 commence the forming process, and thereafter, the pressure applied by the actuators 318 can be reduced as forming by the fingers 100 progresses.

As the forming head 64 continues to move down, the fingertips 102 of the ply sweeper 65 engage and slide over the wings 334 of the presser 316 (FIG. 56), and then form the ply 82 down over the web sections 78 of the mandrel 74 (FIG. 57). The force applied by the pneumatic cylinder 182 that moves the forming head 64 downwardly is greater than force applied to the presser 316 by the linear actuators 318. Consequently, when the presser 316 engages the cap section 76 of the mandrel 74 (FIG. 54), the piston rod 320 begins retracting while linear actuators 318 continue to apply clamping force to the presser 316. FIG. 57 shows the fingertips 102 of the ply sweeper 65 having fully formed the ply 82 down over the web sections 78 of the mandrel 74. Then, similar to the embodiments previously described, the vacuum bag 105 is evacuated, causing the ply 82 to be vacuum formed down onto the flange sections 80 of the mandrel 74.

Attention is now directed to FIG. 59 which illustrates a system for forming contoured composite stiffeners using a plurality of former modules 174 that incorporate the forming heads 64 previously described in connection with FIGS. 44-58. Each of the former modules 174 includes a pneumatic cylinder 182 coupled through suitable directional flow control devices 354, 356 and a pressure regulator 352 to a source of pressurized and filtered air 358. As previously described, the pneumatic cylinders 182 control the displacement of forming heads 64, each of which includes a pair of linear actuators 318, which in the illustrated example, are also pneumatic cylinders 318 that control displacement of the pressers 316. While double acting pneumatic cylinders have been illustrated, hydraulic cylinders or other power operated devices, including electric motors may be employed. Each of the pneumatic cylinders 318 are also coupled to the source of pressurized and filtered air 358 through a pressure regulator 360. The operation of the pneumatic cylinders 182, 318 is controlled by a controller 348 which may include a manually operated switch 349 that controls the up down displacement of the pneumatic cylinders 182, 318. In some applications, a line 350 may be trained along the length of the apparatus spanning the former modules 174 to allow an operator to operate the switch 349.

FIG. 60 broadly illustrates the overall steps of a method of forming a composite stiffener contoured along its length. Beginning at 364, at least one ply 82 of material is placed over a contoured mandrel 74. At 366, a vacuum bag 105 is installed in sealed around the combination of the mandrel 74 and the ply 82. At 368, a forming head 64 is positioned above and aligned with the mandrel 74, thereby aligning the ply sweeper 65 and presser 316 with the mandrel 74. At 370, the presser 316 is extended relative to the ply sweeper 65 using a linear actuator 318. At 372 a portion of the ply 82 is clamped against the mandrel 74 by moving both the presser 316 and the ply sweeper 65 toward the mandrel 74, causing the presser 316 to force a portion of the ply 82 against the mandrel 74. At 374 the ply 82 is swept down over the mandrel 74 while the portion of the ply 82 remains clamped against the mandrel 74. As the ply sweeper 65 moves down over the mandrel 74, the cylinder rod of the pneumatic cylinders retract while maintaining a force on the presser 316. At 376, remaining portions of the ply are vacuum formed onto the mandrel 74 by evacuating the vacuum bag 105. Evacuation of the vacuum bag 105 also compacts the fully formed stiffener. At 378, the forming head 64 is retracted, following which the composite stiffener is further processed (e.g. cured as by autoclave processing.

As previously mentioned, depending on the length of the composite laminate stiffener being produced, it may be necessary to employ a plurality of the forming heads 64, in which case the presser sections 316 a of the forming heads 64 are connected together (see FIGS. 51 and 52). The connected presser sections 316 a essentially form one continuous presser 316 that is used to clamp the plies 82 against the cap section 76 of the mandrel 74 along its entire length, while conforming to the longitudinal contours of the mandrel 74. The above described clamping action provided by the presser 314 prevents lateral displacement, and resultant misalignment of the plies 82 during the subsequent sweeping action by the fingers 100 along the entire length of the plies 82. Thus, the method shown in FIG. 60 may also include additional steps, similar to those shown in FIG. 43, of assembling and aligning a plurality of the former modules 174 (FIG. 37) each having a forming head 64, interconnecting the presser sections 316 a of the forming heads 64 to form a continuous presser 316, aligning the forming heads 64, including the presser sections 316 a, above the mandrel 74, and clamping the plies 82 against the mandrel 74 along its contoured length.

Embodiments of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine, automotive applications and other application where contoured elongate composite laminate stiffeners, such as stringers, may be used. Thus, referring now to FIGS. 61 and 62, embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method 380 as shown in FIG. 61 and an aircraft 382 as shown in FIG. 62. Aircraft applications of the disclosed embodiments may include, for example, without limitation, a variety of composite structural members, including but not limited to stringers. During pre-production, exemplary method 380 may include specification and design 384 of the aircraft 382 and material procurement 386. During production, component and subassembly manufacturing 388 and system integration 390 of the aircraft 382 takes place. Thereafter, the aircraft 382 may go through certification and delivery 392 in order to be placed in service 394. While in service by a customer, the aircraft 382 is scheduled for routine maintenance and service 396, which may also include modification, reconfiguration, refurbishment, and so on.

Each of the processes of method 380 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.

As shown in FIG. 62, the aircraft 382 produced by exemplary method 380 may include an airframe 398 with a plurality of systems 400 and an interior 402. Examples of high-level systems 400 include one or more of a propulsion system 404, an electrical system 406, a hydraulic system 408 and an environmental system 410. Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries.

Systems and methods embodied herein may be employed during any one or more of the stages of the production and service method 380. For example, components or subassemblies corresponding to production process 388 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 382 is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages 388 and 390, for example, by substantially expediting assembly of or reducing the cost of an aircraft 382. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft 382 is in service, for example and without limitation, to maintenance and service 396.

As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of each item in the list may be needed. For example, “at least one of item A, item B, and item C” may include, without limitation, item A, item A and item B, or item B. This example also may include item A, item B, and item C or item B and item C. The item may be a particular object, thing, or a category. In other words, “at least one of” means any combination items and number of items may be used from the list but not all of the items in the list are required.

The description of the different illustrative embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different advantages as compared to other illustrative embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. Apparatus for forming plies of material onto a mandrel having contours, comprising: a ply sweeper comprising a plurality of fingers configured to deflect outwardly to sweep the plies onto the contours of the mandrel; a presser independently displaceable relative to the ply sweeper for pressing a portion of the plies against the mandrel, the presser including a rib connected to at least one powered actuator, and a pair of flexible wings extending outwardly from the rib and engageable with the mandrel; and the at least one powered actuator coupled with the presser for displacing the presser relative to the ply sweeper.
 2. The apparatus of claim 1, wherein the ply sweeper includes a tube having a plurality of slots therein and the plurality of fingers defined between the slots configured to engage and press the plies against the contours of the mandrel.
 3. The apparatus of claim 1, wherein: the powered actuator includes a pneumatic cylinder having a cylinder rod, and a coupling connecting an end of the cylinder rod with the presser.
 4. The apparatus of claim 3, wherein the coupling includes a slot in the presser and a pivotal connection slidable within the slot.
 5. The apparatus of claim 1, wherein: the presser includes a plurality of presser sections attached to each other and arranged end-to-end, and each of the presser sections is formed of a flexible material allowing the presser to conform to the contours of the mandrel.
 6. Apparatus for forming composite plies on a mandrel contoured along its length and having a cap, a pair of webs and a pair of flanges configured to form a hat-shaped stringer, comprising: a frame; a ply sweeper mounted on the frame and configured to sweep the composite plies down onto and over the pair of webs of the mandrel using a plurality of fingers of the ply sweeper configured to deflect outwardly; a presser mounted on the frame and extendable relative to the ply sweeper, the presser being configured to press a portion of the composite plies against the cap of the mandrel, the presser including a rib connected to at least one linear actuator and a pair of flexible wings extending outwardly from the rib and engageable with the mandrel; and the at least one linear actuator mounted on the frame and coupled with the presser for extending the presser relative to the ply sweeper.
 7. The apparatus of claim 6, wherein: the ply sweeper includes a tube having a plurality of slots therein and fingers defined between the slots configured to engage and press the composite plies against the webs of the mandrel.
 8. The apparatus of claim 6, wherein the at least one linear actuator is a pneumatic cylinder mounted on the frame and having a displaceable piston rod coupled with the presser.
 9. The apparatus of claim 6, wherein: the ply sweeper includes opposing sets of spaced apart, flexible fingers having fingertips, and the presser is extendable by the at least one linear actuator beneath the fingertips.
 10. The apparatus of claim 6, wherein: the presser includes a plurality of presser sections attached together and arranged end-to-end, and the presser is formed of a flexible material allowing the presser to conform to the contoured length of the mandrel.
 11. The apparatus of claim 6, further comprising: a coupling between the at least one linear actuator and the presser allowing the presser to conform to the contour of the mandrel.
 12. The apparatus of claim 11, wherein the coupling includes a slot in the presser and a pivotal connection slidable within the slot connecting the presser with the at least one linear actuator.
 13. A method of forming a composite stiffener contoured along its length, comprising: placing at least one composite ply over a mandrel; positioning a ply sweeper and a presser above the mandrel, wherein the ply sweeper comprises a plurality of fingers configured to deflect outwardly to sweep the at least one composite ply onto contours of the mandrel, and wherein the presser includes a rib connected to at least one powered actuator, and a pair of flexible wings extending outwardly from the rib and engageable with the mandrel; extending the presser relative to the ply sweeper using the at least one powered actuator coupled to the presser; clamping a portion of the composite ply against the mandrel, including moving the presser and the ply sweeper toward the mandrel until the presser forces the portion of the composite ply against the mandrel; and sweeping the composite ply down over the mandrel using the plurality of fingers while the portion of the composite ply is clamped against the mandrel.
 14. The method of claim 13, wherein extending the presser includes extending a pair of piston rods.
 15. The method of claim 14, further comprising: retracting the pair of piston rods as the ply sweeper sweeps the composite ply down over the mandrel.
 16. The method of claim 13, further comprising: attaching a plurality of presser sections together end-to-end; and pivotally coupling the presser with the powered actuator to allow the presser to conform to the contoured length of the mandrel.
 17. The method of claim 13, wherein clamping a portion of the composite ply against the mandrel includes applying a force to the presser using the powered actuator.
 18. The method of claim 13, wherein clamping a portion of the composite ply against the mandrel includes centering the presser on the mandrel using the flexible wings of the presser. 